Various methods are used to dispose of tires. For example, they can be simply ground up or mulched, or used for fuel referred to as tire derived fuel (TDF). Tires have been used as fuel in the cement industry in cement kilns, in boilers in pulp and paper mills, in power plants of electric utilities and in industrial boilers. When used for fuel the tires are typically first ground up or shredded and then placed in an incinerator at high temperatures, for example, above 1500° F., and incinerated as, for example, in US application publication no. US 2004/0025763.
There are a number of problems, however, with incinerating tires or using tires as fuel. One is the metal in the tires. The metal in the tires tends to clog feed systems in the pulp and paper industry. As a result, the pulp and paper industry needs to remove the metal, or de-wire the tires, before using them as fuel. Similarly, the tires must be de-wired and typically ground up before use by electric utilities. Also, when grinding the tires, tiny fines of metal from the steel bead ring in the tires and the steel belts in radial tires are left in the ground up material.
Other problems with incinerating tires for fuel involve environmental issues with air emissions that can include dioxins, furans, carbon monoxide, sulfur dioxide, hydrogen sulfide, nitrous oxides (NOx), carbon dioxide, and/or particulates. There can also be problems with disposal of resulting ash that can include metals and heavy metals from the tires, such as zinc, chromium, cadmium and lead. Moreover, these methods of disposal also do not reclaim for reuse any of the various components of the tires.
There is a need, therefore, for an improved system for not only disposal of used tires, but also for recovery of the tire components for reuse. Additionally, there is a need for more energy efficient disposal of tires and recovery of tire components for reuse.